Organic materials commonly referred to as photoresists are recording media on which information can be recorded in the form of a surface relief pattern. Such media, when exposed to a light pattern, change their solubility characteristics in those area struck by the light. Photoresists may be developed by contacting them after exposure with a solvent which dissolves the more soluble portions, leaving the less soluble portions in a relief pattern which corresponds to the information contained in the light pattern. Negative photoresists are initially soluble in the developer solution and the exposed portions become insolubilized. Positive photoresists are initially insoluble and become soluble in the exposed portions.
Recently, suitably modulated electron beams have also been utilized for recording information in the form of relief patterns. Electron beams, by virtue of their shorter effective wavelengths and greater depth of focus, can thus record information at higher resolution or density than can light beams.
Several materials that are known to be photosensitive are also sensitive to electron beams. Among these are certain members of a class of naphthoquinone-(1,2-)diazide sulfonic acid esters which have the general formula: ##STR1## wherein X and Y are N.sub.2 or O and R is selected from certain aryl, substituted aryl or heterocyclic radicals. These compounds are disclosed, for example, in U.S. Pat. No. 3,046,118. These light sensitive esters are admixed with an alkali-soluble resin to form a photoresist composition.
The compound having the formula: ##STR2## in admixture with the corresponding monoester and triester byproducts, combined with a cresol-formaldehyde resin available as Alnovol 429-K from Chemische Werke Albert, of Wiesbaden-Biebrich, Germany, is available commercially as AZ 1350 photoresist from the Shipley Co. This material, while effective as an electron beam resist, has deficiencies in reproducibility and sensitivity.
Another compound of this type which has improved sensitivity to electron beams after suitable purification has been disclosed by Ross et al, in U.S. Pat. No. 3,852,771. The electron beam sensitive compound has the formula: ##STR3##
Since a high degree of purity and batch-to-batch reproducibility is required for electron beam recording media of consistent performance, this compound is purified, preferably by a reprecipitation step followed by a recrystallization step. Various other compounds of this series have also been tried as sensitizers for electron beam resists, but have been found to be unsatisfactory, either because of low sensitivity; because the compounds cannot be purified to the required level; or because the compounds, after purification, have been too insoluble in the inert solvents which have satisfactory release properties for the spinning of high quality films having good uniformity and smoothness.